1. Field of the Invention
The present invention relates to an organic electroluminescent display.
2. Discussion of the Related Art
Many concerns are focused on an organic EL (electroluminescent) display as a
flat display for next generation. The EL display is provided to a small mobile apparatus such as a mobile phone and is in common use.
The organic EL display employed to the mobile apparatus requires long life span and low electric consumption. However, the organic EL display currently used is not satisfied with the condition.
One of the reasons why the organic EL display does not have long life span and low electric consumption is a use of a substrate having a high refractive index.
Namely, most of light generated by using the substrate having the high refractive index is totally reflected because a part of the light is emitted.
In general, total inner reflection of a glass substrate and a loss of light from doparo effect reach about 80%. Therefore, brightness of the display is increased with a little electric consumption if the loss of light is reduced.
Not only time of using the mobile apparatus is elongated but also the life span of the organic EL display is elongated because brightness of the display is increased with a little electric consumption.
Therefore, a method of roughening a surface of the substrate, a method of forming a pattern with projections on the surface of the substrate, and a method of using semicircular lens in a millimeter size are employed as a method for reducing a light loss resulted from the inner reflection and doparo effect, and increasing the light efficiency.
However, the methods have problems that a pattern of light radiation is changed, a displayed image is blurred, and manufacturing is difficult.